In the manufacturing process of products in which a fluid is hermetically sealed in a container, such as in canned foods, in order to manage the quality of the contained liquid, it is indispensable to ascertain the oxygen content in the headspace within the container, and the amount of oxygen dissolved in the fluid. As a devices to measure the amount of oxygen used in this kind of application, there has been a proposal for a device in which a headspace oxygen measuring device and a device for measuring the amount oxygen dissolved in the fluid are arranged in a sampling line that branches from the production line, canning containers are suitably pulled from the production line to the sampling line, samples of headspace gas and the contained fluid are extracted by piercing that canning container with needles or nozzles from the respective measuring devices, and the oxygen content is measured by analyzing these samples (for example, refer to Patent Publication 1). In addition, there have been various proposals for methods and devices to extract gas or fluid samples by piercing hermetically sealed contains such as cans (for example, refer to Patent Publications 2 to 4). Electro-chemical oxygen concentration meters, for example, polarograph-type oxygen concentration meters, which lead the oxygen in the sample between electrodes, cause a chemical response, and detect the oxygen based on the current flowing between the electrodes, have been used as means to detect the concentration of oxygen within samples (refer to Patent Publications 3 and 4).
Concentration meters that use the paramagnetism of the oxygen, and concentration meters that use fluorescent material are well-known as oxygen concentration meters that differ from electrochemical oxygen concentration meters. The latter concentration meter utilizes the phenomenon that the fluorescent energy that the fluorescent substance generates is consumed as the excitation energy of the ground state oxygen present around that fluorescent substance, thus quenching the fluorescent light, and the oxygen concentration is specified from the intensity and duration of the fluorescent light. Well-known as this type of concentration meter are concentration meters, in which a fluorescent substance is arranged on the tip of a probe, the fluorescent substance is irradiated with excitation light though optical fibers to produce fluorescent light, and this fluorescent light is led by optical fibers to a photoelectric conversion circuit positioned behind (for example, refer to Patent Publication 5). Moreover, examples of applications of oxygen concentration meters using fluorescent light include a proposal for a device to measure the required amount of biological oxygen in sample water by inserting a ride guide provided with a fluorescent oxygen tip into a culturing container filled with sample water (refer to Patent Publication 6).
[Patent Publication 1] Japanese Laid-open Patent No. H7-58244
[Patent Publication 2] U.S. Pat. No. 3,600,697
[Patent Publication 3] Japanese Laid-open Patent No. H1-113659
[Patent Publication 4] Japanese Laid-open Patent No. H4-176636
[Patent Publication 5] Japanese Laid-open Patent No. H10-132742
[Patent Publication 6] Japanese Laid-open Patent No. H11-242025